Pr6O11-Coated High Capacity Layered Li[Li0.17Ni0.17Co0.10Mn0.56]O2 as a Cathode Material for Lithium Ion Batteries

A Li-rich layered oxide Li[Li0.17Ni0.17Co0.10Mn0.56]O-2 is synthesized and coated with Pr6O11 by a chemical deposition method. The pristine and the Pr6O11-coated Li[Li0.17Ni0.17Co0.10Mn0.56]O-2 cathodes are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and charge-discharge measurements. After coating of Pr6O11, the bulk crystallographic structure, morphology and grain size of the layered Li[Li0.17Ni0.17Co0.10Mn0.56]O-2 are not essentially changed. Compared to the pristine Li[Li0.17Ni0.17Co0.10Mn0.56]O-2 cathode, the Pr6O11-coated Li[Li0.17Ni0.17Co0.10Mn0.56]O-2 cathodes coated with suitable thickness exhibit higher discharge capacity with lower irreversible capacity loss, better cyclability and higher rate capability. Especially, 5 wt% Pr6O11-coated sample displays the highest capacity (277.9 mAh g(-1) at 0.05 C rate), the best rate capability (196.2 mAh g(-1) at 1C rate) and the best cyclability (capacity retention of 91.2% in 50 cycles). Of particular concern is the polarization behavior of Pr6O11-coated cathodes coated with suitable thickness. Impedance analysis demonstrates that the rate capability of Pr6O11-coated cathodes are mainly affected by the lithium ion diffusion resistance through the surface layer (solid-electrolyte interfacial (SEI) layer and Pr6O11 coating), while influences of the faradaic charge transfer resistance is negligible. This work shows a promising approach to improve the electrochemical performance of Li-rich layered oxides by surface modification of semiconductor materials. (C) 2014 The Electrochemical Society. All rights reserved.